Centrifuge tube and method of centrifuging



March 24, 1959 7 CENTRIFUGE TUBE AND METHOD OF CENTRIFUGING Filed May 22. 1956 N. G. ANDERSON d- 22/ E2 5 22d ENTOR 0 ATTORNEYS AZyNzJERsa/v BY 7% 01M United States Patent CENTRIFUGE TUBE AND METHOD or CENTRIFUGING Norman G. Anderson, Oak Ridge, Tenn., assignor to Owens-Illinois Glass Company, Toledo, Ohio, a corporation of Ohio Application May 22, 1956, Serial No. 586,549 4 Claims. Cl. 233-26) The present invention relates to centrifugation and more specifically to an improved centrifuge tube and 'method of centrifuging to separate particles within liquid solutions. This invention is \especially applicable to studies of biological solutions such as breis and layered systems in which during and after centrifugal fractionationtheir minute particles may be examined.

In various centrifuge procedures liquidus materials are jrotated in cylindrical tubes 'to effect fractionation of constituents based on their characteristic densities. With regular cylindrical tubes an. appreciable amount of sedivmented material strikes the tube sidewall and temporarily y adheres thereto before it reaches the bottom or its proper lidensitylevel. Observation has shown that in some inchondria where precise centrifuging and a continuous density gradient are "required for their satisfactory separation.

Accordingly, it is an object of this invention to provide an improved centrifuge tube having a modified sector shape which facilitates improved fractionation of layered solutions during centrifugal analysis.

Another object ofthis invention is to provide a centnfuge tube suitable for gravitational fractionation of particles with minimum turbulence and greater optical resolution for magnified examination thereof, both during and after rotation.

Another object of thisv invention is to provide a centrifuge tube which in use has sidewalls substantially parallel to lines of centrifugal force radially projecting from the axis of rotation of centrifugation apparatus.

Another object of this invention is to provide an im' proved glass centrifuge tube having a hemispherical bottom, an elliptical opening, and sidewalls having inner surfaces substantially parallel to radial lines from the rotational axis of centrifuging apparatus,

Another object of this invention is to provide an improved method of centrifugation utilizing a glass centri- -:fuge tube having a modified sector'shape which is positioned and'rotated in centrifugal'apparatus with projections of inner surfaces of its sidewalls intersecting the axis of rotation thereof for increased fractionation of small particles.

The specific nature of this invention, as well as other objects and advantages thereof, will become apparent to one skilled in the art from the following detailed description taken in conjunction with the annexed set of drawings on which, by way of preferred example only, is illustrated one embodiment of this invention.

On the accompanying drawings:

Fig. 1 is an elevational view of centrifuge apparatus and tube embodying this invention.

horizontal plane.

2,878,994 Patented Mar. 24, 1959 Fig. 2 is a plan view of the apparatus and tube taken along the line 2-2 of Fig. l.

Fig. 3 is an enlarged elevational view of the tube alone.

Fig. 4 is a vertical sectional view taken along the line 4-4 of Fig. 3. p

Fig. 5 is atop plan view of the tube.

Fig. 6 is a horizontal sectional view taken along the line 66 of Fig. 4.

Fig. 7 is a similar view taken along the line 7-7 of Fig. 4. 1

Fig. 8 is a horizontal sectional view of the tube and retention device taken along the line 2-2 of Fig. 1.

Referring now to the drawings, the apparatus as shown onFig. 1, consists of a centrifuge machine 10 having a vertical rotatable shaft 11 which is driven at varied speeds of rotation by motor M operating through gear box 12.

A horizontal arm 13 is rigidly attached in its center portion to the, upper end of shaft 11 for rotation in a A yoke 14 is provided at each end of arm 13 to support a centrifuge cup 15 shaped to retain a centrifuge tube 16. The cup 15 is normally cylindrical and fabricated of metal with an opening at its upper end and a layer of cushioning material 17 within its bottom. Cup 15 has two stud members 18 extending from opposite sides of its upper portion which are free to rotate in recesses 19 in the sides of yoke 14. Thus cup 15 and tube 16 are conjunctively able to freely rotate about the axis of stud members 18 through a right angle from a vertical position at rest to a horizontal position when rotating (as shown on Figs. 1 and 2).

Tube 16 has a regular cylindrical contour when viewed in one elevational view (as shown on Fig. 3) with oppositely disposed parallel surfaces 22a which may be fitted into the interior of cup 15. Tube16 has a modified sector shape at right angles to its cylindrically appearing contour with a hemispherical bottom 20 sealing its lower end. All transverse planes passed through the side walls of tube 16 from regularly circular to elliptically shaped areas develop a series of ellipses having constant major axes and decreasing minor axes to the top of the tube. Bottom 20 and sidewalls 22 of tube 16 are of essentially uniform thickness (as shown on Fig. 4) and sidewalls 22 terminate at an elliptical-shaped opening 21. The major axis of elliptical opening 21 is substantially equal to the inner diameter of bottom 20 and this dimension is essentially uniform throughout the length of the tube parallel sidewalls 22a. Its minor axis is continuously diminishing throughout the length of converging sidewalls 22b.

Tube 16 is preferably composed of borosilicate lead,

flint, or other type of glass through which contained solutions 28 may be viewed'microscopically without distortion or aberration while eitherstationary or rotating. Projections 27 of the converging sidewalls 22b intersect the axis of rotation of vertical shaft 11 in the horizontal rotational plane of centrifuge machine 10. The'sidewalls 22a and 22b of tube 16 are generated by an annular locus of lines respectively parallel to theplane of rotation and extending from the periphery of hemispherical tube bottom 20 to the rotational axis of shaft 11. Thus, projections 27 are perpendicular to the axis of rotation of shaft 11 and provide tube sidewalls 22a and 22b which are parallel to centrifugal lines of force generated by machine 10.

The top view of tube 16 (as shown in Fig. 5) illustrates the lower and larger end of tube 16 as hemispherical in contour and the smaller end terminating at the ellipticalshaped opening 21. The sidewalls 22b of tube 16 uniformly converge toward elliptical opening 21 in a varied series of ellipses (as shown on Figs. 6 and 7) having the same major and diminishing minor axes. The maximum included angle of converging sidewalls 22b which lie in the plane perpendicular to the plane of rotation is approximately 8, but maybe varied through wide limits depending upon the particular size and design of both machine 10 and tube 16. Tube 16 is oriented within cup and the centrifuge machine 10 in proper relation to the rotational axis of shaft 11 with the maximum included angle of its sidewalls 22b in its rotational plane. Expressed in another manner, extensions of the inner surfaces of converging and parallel sidewalls 22b and 22a respectively are parallel to the plane of rotation and intersect the axis of rotation when cup 15 and tube 16 are conjunctively spun about shaft 15.

The opening of cup 15 is covered by a cap 23 after tube 16 is positioned therein. A retainer ring 24 is arranged around the upper portion of tube 16 to accurately locate and retain the elliptical opening 21 particularly in its shorter dimension. Ring 24 may be attached to cap 23 by two or more rods 25 and may also be tightly fitted to tube 16 for its convenient removal from cup 15.

A window 26 of desired size and shape is provided in the side of cup 15 through which contained solutions may be directly observed during centrifugation. A strobo- 'scopic lighting system may be connected to a contactor on shaft 11 to furnish a stable image for observation through an enclosing jacket (not shown) at varying speeds of rotation. V I

Solutions 28 containing particles of varied densities are placed in tube 16 which in turn is properly arranged in cup 15. Tube 16 is positioned so that projections 27 of the inner surfaces of sidewalls 22a and 22b approximately intersect the rotational axis of shaft 11 when tube 16 is in a horizontal rotational plane. When more than one tube 16 is employed, each is similarly located. It is preferable that projections 27 of inner surfaces of the sidewalls 22a and 22b be preciselylocated to intersect the rotational axis to minimize turbulence and contact between particles and tube sidewalls. Control over rates of acceleration, angular rotation, and deceleration may be maintained to achieve optimumseparation for microscopic or other forms of analysis.

Layered solutions 28 within tube 16 are then subjected to centrifugation by machine 10 to obtain fractions of varying densities with no cross contamination of the separated particles. Varied speeds of rotation and rates of acceleration and deceleration. may be employed depending upon the properties of the systems to be separated. Centrifuge tube 16permits quantitative separation of all fractions with minimum contact of particles with the tube surfaces during their movement to their respective density levels. Tube 16 also permits recovery of all fractions after centrifugation by introducing a more dense material into the bottom to displace lighter fractions. d

In cellular studies, where smaller particles need only be moved a. relatively short distance for separation, high gravitational fields are. not required. However, the subject tube and method are equally applicable to both high and low gravitational applications. The characteristics of the tube shape and orientation readily lend themselves to a reproducible system suitable-for obtaining accurate analytical results. It is known that in conventional centrifuging. methods, difiiculties arise during centrifugation becauseof changes in tube orientation. The present tube cannot shift due to rotational vibration to produce erroneous results. With all of its sidewalls in parallel alignment with generated lines of centrifugal force, that is, both radial in a horizontal plane and in straight lines perpendicular to the axis of rotation, little or no extraneous disturbance of particle movement is produced. The present tube may be readily assembled in the illustrated or similar retention apparatus in correct alignment to achieve precisional fractionation of solutions. Furthermore, centrifuge tubes constructed in accordance with this invention have been found to resist breakage under centrifugal stress to a remarkable degree over conventional tubes. This is due to the fact that the lines of centrifugal stress are parallel to the walls with the result that the glass is only under compression and is not subjected to bending forces.

Additional modifications may be resorted to within the spirit and .scope of the appended claims.

I claim:

1. A centrifuge container for centrifugal analyses comprising a hollow tube having a cylindrically bounded concave-convex bottom and integral side walls terminating in an elliptically shaped opening, the major axis of said opening being essentially equal to the diameter of said bottom and substantially greater than the minor axis of said opening, said side walls constituting essentially straight line projections between said bottom and said opening.

2. A centrifuge container for. centrifugal analyses comprising a hollow tube having a hemispherically shaped bottom and integral side walls terminating in an elliptically shaped opening, the major axis of said opening being approximately equal to the diameter of said bottom and substantially greater than the minor axis of said opening, said side walls constituting straight line projections between said bottom and said opening.

3. A centrifuge apparatus comprising in combination a container tube for rotation about a centrifuge axis, mounting means for permitting the container tube to rotate in a radial orbit about the centrifuge axis but preventing rotation of the container tube about its own major axis during centrifugation, operative means to rotate said container tube and mounting means during centrifugation, said tube being so shaped that during centrifugation its outer end is closed, its inner end is opened, and the side walls lie essentially in a surface generated by a line perpendicular to the centrifuge axis moving in a path with the inner end of the line moving along this axis and the outer end along the periphery of the closed end, whereby all material in the tube is afforded during centrifugation a path of movement directly toward the closed outer endv of the tube without interposition of any of the tube side walls.

4. The combination defined in claim '3, wherein said centrifuge tube is comprised of glass and has a hemispherically shaped bottom and an elliptically shaped opening.

References Cited in the file of this patent UNITED STATES PATENTS D. 97,890 Ballard Dec. 24, 1935 911,523 Piers Feb. 2, 1909 2,198,256

Levy Apr. 23, 1940 

